The present invention relates generally to pumping arrangements, and more particularly to pumps which are completely self-draining when not being operated.
There are already known various pump constructions, among them such which are often being referred to as self-draining pumps. In pumps of this type, all of the liquid that is being pumped by the pump while in operation is drained out of the pump when the pump is not being operated. The reason for this may be, for instance, when the pump is being used as a recirculating pump in conjunction with a whirlpool bath, a spa, or a similar facility in which water is being recirculated, to assure that no stale water will remain in the pumping system where it could promote growth of bacteria, fungi or mildew with possible attendant unpleasant odor, contamination or even possibly a health hazard. This potential problem has already been previously recognized, and it is for this and similar reasons that the so-called self-draining pumps have been developed.
So, for instance, there has already been proposed a self-draining pump construction in which a small aperture is provided in the pump housing assembly, this aperture communicating with the lowermost region of the pumping chamber and being connected, during the installation of the self-draining pump, to a drain, so that some of the water from the pumping chamber, which constitutes the high-pressure side of the pump, is drained into the drain even during the normal operation of the pump. Obviously, this is highly wasteful of energy since some of the usually heated water is drained out of the system and may have to be replenished with additional water which usually has to be heated before being introduced into the system. This energy waste is additional to the wasted energy resulting from the fact that some of the previously pressurized water goes into the drain.
On the other hand, it has also already been proposed to provide an adaptor for a pump with a central axial inlet nipple, which adaptor bounds an adaptor passage that leads downwardly from the central passage of the inlet nipple to an elevation low enough to be in substantial horizontal alignment with the bottom region of the pumping chamber of the pump, and to provide a draining passage with a relatively small cross sectional area in the pump housing and/or the adaptor between the bottom region of the pumping chamber and the lowermost region of the adaptor passage. However, experience with pumping arrangements of this type has shown that numerous problems resulting from the provision of the separate adaptor, including but not limited problems with sealing the additional interface between the adapter and the lid of the pump housing on which the adator is mounted, are encountered in this particular pump construction.